Railway signaling system



H. A. THOMPSON RAILWAY SIGNALING SYSTEM web 24, 1942.

Filed Jan.

'fiE .EQNANT RECTIEIER UNITS Patented Mar. 24, 1942 2,277,4tt V RAILWAY SIGNALING SYSTEM Howard A. Thompson, Edg'ewood, Pa., assignor to I The Union Switch & Signal Company, Swissvale, Pa., a' corporation of Pennsylvania Application January 13, 1940, Serial No. 313,739

3 Claims.

My invention relates to railway signaling systems and particularly to improved means for use on railways employing electric current for propulsion purposes to protect against false energization of a track relay in the event one of the insulated joints separating two track sections becomes defective.

Where electric current is employed for propulsion purposes it is customary to employ the track rails to provide a return path for the propulsion current, and it is necessary to provide impedance bonds to conduct propulsion current around the insulated joints which divide the track rails into track sections for signaling purposes.

Under normal conditions, with the insulated joints in both rails at the junction between two track sections intact, the impedance bonds permit propulsion current to freely flow between the rails of the adjoining track sections, while they substantially prevent flow of signal control current between rails of these sections.

However, as the impedance bonds have been employed heretofore, in the event the insulated joint in either of the two track rails separating two adjacent track sections becomes defective, the impedance bonds operate to permit flow of signal control current from the track rails of .the section in the rear of the defective joint to the rails of the section in advance of the defective joint. The current supplied in this manner to the rails of the section in advance of the defective joint will effect operation of some types of track relays, particularly the single element code following track relay, and may cause the track relay to condition the signal controlled thereby to im' properly display a proceed indication.

In the typical arrangement of impedance bonds heretofore employed, each track section has been provided at each end with an impedance bond comprising an inductive winding having one of its end terminals connected to one track rail, and having its other end terminal connected to the other track rail, while each winding has had a center or neutral terminal which has been connected to the center or neutral terminal of the winding of the bond associated with the adjacent end of the adjoining track section.

As the neutral or center terminal of the winding of one bond is connectedto the neutral or center terminal of the bond of the adjacent section, any signal control current which flows through one-half of the winding of one bond will flow to the center terminal of the connected bond and will then flow in equal magnitude to both rails of the adjacent section so that it does not have any effect on the track relay connected to the track rails of that section.

If, however, one insulated joint becomes defective, a difierent-condition is present and the impedance bonds operate to supply signal control energy from the rails of the section on-one side of the defective joint to the rails of the section on the other side of the defective joint. This permits signal control energy supplied to the section in the rear of an occupied section to feed to the rails of the occupied section where it may cause operation of the track relay of the occupied section.

When an insulated joint becomes defective the entire winding of the impedance bond at the forward or exit end of the section in the rear of the defective joint forms the primary winding of an autotransformer, while the half of the winding which is connected to the rail having the defective joint therein forms the secondary Winding of the transformer. One end terminal of this secondarywinding is connected by the neutral bond, tothe center terminal of the winding of the adjacent bond, that is, to one end terminal of one-half .of the winding of the bond at the rearward end of the section in advance of the defective joint, while the other end terminals of the two halves of the two impedance bond windings are connected together by the track rail through the defective insulated joint.

The half of the winding of the bond at the rearward orentrance end of the section in advance of the defective joint operates as the primary winding of an autotransformer, while the entire winding of the bond forms the secondary winding of the transformer.

As a result of the relationship outlined above 'in case one insulated joint is defective on the supply of alternating current signal control energy to the rails of the rearward section, current flows through the entire winding of the impedance bond at the forward end of the section and induces energy in the half, of the winding forming the secondary of the autotransformer. This secondary then supplies energy over the neutral conductor and the rail having the defective joint therein to the half of the winding of the bond at the rearward end of the forward section which forms the primary winding of an autotransformer.

On the supply of energy to the half of the winding of the bond of the forward section, this portion of the winding serves as the primary winding of an autotransformer, while the entire winding constitutes the secondary of the autotransformer and energy is induced in this winding from which it is supplied to the rails of the forward section. This energy will cause picking up of the contacts of the track relay of the forward section with resultant improper display of a proceed indication by the signal for the forward section at times when the forward section is occupied.

It is an object of this invention to provide means for use on a railroad having a plurality of tracks to interconnect the windings of the impedance bonds of the track sections in such manner that breaking down of one insulated joint separating two adjoining track sections will not result in the supply of signal control current between the rail of the sections On opposite sides of the defective joint.

A further object of the invention is to provide novel means to interconnect the impedance bonds of the track sections of a railroad having a plurality of tracks to eliminate the autotransformer action of th bonds in the event an insulated joint is defective.

Another object of the invention is to provide a railway system employing electric current for propulsion purposes and having a signaling system which is unaffected by breaking down of one insulated joint separating two track sections.

A further object of the invention is to provide an improved railway signaling system.

I shall describe two forms of apparatus embodying my invention and shall then point out the novel features thereof in claims.

In the drawing, Fig. 1 is a diagram illustrating a portion of a two track railroad employing equipment embodying this invention, and

Fig. 2 is a diagram showing the manner of applying the invention to a three track railroad.

Referring to the drawing, there is shown in Fig. 1 thereof a diagram of a stretch of two track railroad equipped with apparatus embodying my invention. The railroad shown in Fig. 1 employs electric current for propulsion purposes, and has tracks A and B over which traffic normally moves in the directions indicated by the arrows, that is, from left to right on track A, and from right to left on track B.

The track A has track rails I and 2, while track B has track rails 3 and 4. The track rails of each track are divided by insulated joints into the customary block or track sections for signaling purposes, while the track rails of each of the track sections form a part of a track circuit of the usual character. One complete track section and portions of two other track sections in each of the two tracks are shown in the drawing, the sections in track A being identified as IIT, IZT, and I3T, and the sections in track B being identified as I4T, I5T and IST.

The track stretch may be equipped with any suitable form of signaling system employing alternating current in the track circuits of the various track sections.

One form of signaling equipment which may b employed is shown in Fig. 1 of application Serial No. 210,744 of F. H. Nicholson and L. R. Allison, filed May 28, 1938, for Railway traffic controlling apparatus, now U. S. Letters Patent No. 2,237,788, granted April 8, 1941.

The rails of each of the track sections form a part of a track circuit to which coded alternating current signal control energy is supplied at the exit or leaving end of the track section from the secondary winding of track transformers designated TT with a prefix corresponding with that of the associated track section. The circuits for supplying current from the track transformers include the usual current limiting reactors 1.

Each of the track sections includes a track relay designated TR. together with an appropriate prefix. The track relay is located at the entrance end of the track section and may be of any suitable type. As shown, the relay is of the direct current type having its winding connected to the track rails of the associated track section through a suitable resonant unit RU shown diagrammatically in the drawing.

Each of the resonant units RU comprises a transformer, a capacitor and a reactor so arranged and proportioned as to freely pass energy of the frequency employed to control the signals, and so as not to pass propulsion current of a different frequency. Each unit includes, in addition, a rectifier which converts into direct current the alternating current which is supplied through the unit.

Each of the track sections has at each end thereof an impedance bond 6 of the usual construction having a winding having its end terminals connected to the track rails of the track section, while the winding of each impedance bond is provided with a center or neutral terminal.

In the usual arrangement heretofore employed the center terminal of the winding of the bond at the end of a track section is connected by a neutral connector to the center terminal of the winding of the bond at the adjacent end of the adjoining section. For example, as heretofore arranged the center terminals of th windings of the bonds at the forward end of section I IT and at the rearward end of section I2T have been connected together by a neutral connector.

In the arrangement provided by this invention, however, the center or neutral terminal of the winding of each impedance bond is connected by a neutral connector to the center or neutral terminal of the bond associated with a track section in a different or adjoining track.

Referring to Fig. l of the drawing, it will be seen that the center terminal of the winding of the impedance bond 6 at the rearward end of section I2T in track A is connected by neutral connector 20 to the center or neutral terminal of the winding of the impedance bond 6 at the rearward end of section I6T in track B. Similarly, the center terminal of the winding of impedance bond 6 at the forward end of section I IT in track A is connected by neutral connector 2| to the center terminal of the winding of the impedance bond 6 at the forward end of section |5T in track B.

In like manner the neutral terminals of the windings of the impedance bonds at the forward ends of sections I 2T and MT are connected together by a connector 2|, while the neutral terminals of the windings at the rearward ends of sections I3T and I5T are connected together by a connector 22.

While the connections between the impedance bonds for one track section-in each of the two tracks in the track stretch have been shown, it should be understood that some or all of the other impedance bonds in the track stretch are interconnected in the same manner.

It is understood also that the rails of tracks A and B are connected together at appropriate points by suitable cross bonds. The cross bonds ing of the two rails of section 121 in'multiple,

comprisea winding 8 which is connected between thence through-a path consisting of the two rails the railsof section I3T'and'a similar winding 8 connected between the rails of section I4T,-while the center or neutral terminals of these windings are connected together by a wire 9.

The arrangement of impedance bondconnections provided by this invention eliminates the possibility of signal control-energy feeding from the track rails of one section to the track rails of an adjoining section in the event an insulated cation to supply energy through the transforrner IITT to the rails of section HT.

If at this time the insulated joint 5-in track rail I separating sections HT and I 2T is defective there will be a direct connection between the lower half of the winding of each of-the impedance bonds 5 on opposite sides of the de-- fective joint through track rail I over the defective joint.

However, since the center or neutral terminals of the windings of the bonds 6 on opposite sides of the defective joints are not connected together, the lower portions of these windings cannot functidn as the secondary and primary windings of autotransformers in the manner explained in detail above, and accordingly energy does not :feed from the rails of section HT to the track relay IZTR over the defective joint. The contacts of the track relay IETR, therefore, remain released and the signal I28 continues to display its stop indication. I

The equipment operates in the same manner to prevent the supply of signal control current between the rails of adjoining track sections in the event the insulated joint 5 in the -other rail of track A or in either of the rails of track B is defective.

The impedance bond connections provided by this invention are also arranged in such manner that the path for the flow of propulsion current through the track rails is unimpaired.

If it is assumed that the source of propulsion current is located some distance to the left of track section IZT, the return path for propulsion current for a locomotive located in section IZT is traced through rails I and 2 of track section I2T, thence through the two end portions of the winding of the impedance bond 6 at the rearward end of section IZT, and through the neutral bond 26 to the center terminal of the winding of the bond 5 at the rearward end of section HST. The current then flows through the two end pertions of that winding to the track rails 3 and 4 of section ItT of track B, and then to the source of current.

If the source of current is not connected directly to the rails 3 and 4 of section IBT the current will flow through the rails of section It to the power source through a path similar to that traced above.

As stated above, it is contemplated that cross bonds of the usual type interconnect the rails of the tracks A and B at approximately the same intervals as are customary on electrified railways.

Accordingly, the propulsion current for a train in section IZT will flow through a path consistplayed.

of section IGT in multiple. When a cross bond is reached the current thereafter 'flows through the four rails of tracks Aand B in multiple to the source of energy.

Itwill be seen,'therefore, that with the impedance bond connections provided by this inrails in multiple.

In Fig. 2 of the drawing-I have shown means to interconnect the impedance bonds of the sections of a three track railroad to protect against improper operation of the signal system for each of the tracks in the event one insulated joint separating two track sections is defective.

The railroad shown in Fig.2 is similar'to that shown in Fig. l and employs electric current for propulsion purposes, while it may be'provided with signaling equipment similar to that shown in Fig. l to govern movement of trains over each of the three tracks.-

As shown. there are three tracks identified as C, D and E, the rails of each track being divided by insulated joints 5 into the usual track sections, while each track section has at each end an impedance bond 6 havinga winding having its end terminals connected to the track rails of the track section.

The center terminal of the winding of the bond 6 at the left-hand side of the insulated joints 5 in track C is connected by neutral connector 24 to the center terminal of the winding of the bond 6 at the right-hand side of the insulated joints 5 in the'track D.

Similarly, the center-terminal of the winding of the bond 6 at the left-hand side of the insulated joints '5 in track D is connected by neutral connector 25 to the center terminal of the winding of the bond 6 at the right-hand side of the insulated joints in track E.

The center terminals of the windings of the bonds 6 at the right-hand side of the joints 5 in track C and at the left-hand side of the joints 5 in track E areconnected by neutral connector 26.

It is contemplated that the rails of tracks C, D and E be connected together in the usual manner by cross bonds, not shown, located at suitable points in the track stretch.

The operation of the equipment shown in Fig. 2 is substantially the same as that shown in Fig. 1 both with respect to the circuits for propulsion current and for the signal control current and a detailed explanation thereof is unnecessary.

If the track stretch includes more than three tracks the windings of the impedance bonds may be connected together in a manner similar to that shown in Figs. 1 and 2.

From the foregoing it will be seen that this invention provides means applicable to an electrified railroad having a plurality of tracks to interconnect the impedance bonds to prevent improper operation of the signaling system in the event one insulated joint is defective.

It will be seen also that when the impedance bonds are interconnected in the manner contemplated by this invention that the path for the flow of propulsion current is not impaired,

and is of substantially the same value as when the impedance bonds are interconnected in the usual manner.

The method provided by this invention for interconnecting impedance bonds to prevent improper operation of the signals in the event one insulated joint is defective is particularly useful where the signaling system is of the type employing coded current in the track circuits and where single element code following track relays are employed. This is the type of signaling system shown in Fig. l of the drawing. However, the invention is not restricted to use with this type of signaling system, and it may be employed with any form of railway signaling sys-,

rear track sections, impedance bonds one connected across the rails of each section, a conductor connecting the mid point of the bond for the forward section of one track with the mid point of the bond for the forward section of the other track, a second conductor insulated from the first conductor and connecting the mid point of the bond for the rear section of the one track with the mid point of the bond for the rear section of such other track, and a track circuit for each section of each track including a source,

of alternating current connected across the rails and a track relay receiving energy from the rails.

2. In combination, a stretch of railway track "having a pair of tracks, the rails of each track being divided by insulated joints into track sections, the joints'between the sections in said tracks being located at substantially the same point in the track stretch, a source of alternating current connected across the rails of each section, a track relay for each section having a winding receiving energy from said source over the rails of such section, impedance bonds one connected across the rails of each section, a first conductor connecting the mid point of the bond for the section of one track at one side of a point of division between the sections in said tracks with the mid point of the bond for the section of the other track at the other side of said point of division between the sections in said tracks, and a second conductor insulated from the first conductor and connecting the mid point of the bond for the other section of said one track with the mid point of the bond for the other section of the other track.

3. In combination, a stretch of railway track having a plurality of tracks and employing electric current for propulsion purposes, each track being divided by insulated joints into track sections, the joints between the sections in said tracks being located at substantially the same point in the track stretch, a source of alternating current connected across the rails of each section, a track relay for each section having a winding receiving energy from said source over the rails of such section, impedance bonds one connected across the rails of each section, and a plurality of conductors each connecting the mid point of the bond associated with the track section in one track at one side of the point of division between the sections in said tracks with the mid point of the bond associated with the track section in another track at the other side of the point of division between the sections in said tracks, said conductors being insulated from each other and each connecting a different pair of bonds.

HOWARD A. THOMPSON. 

